Article working apparatus



-.1 ,pril2.1946. V Q MCC/1N 2,398,906

y y ARTICLE WORKING APPARATUS Filed May 13, 1943 i 1 i l l Y i K I i 33 Wilmink? n l l" E i W -.119 il I v1/wmf? C. 6. M0634 //vA Patented Apr. 23, 1946 ARTICLE WORKING APPARATS Cecil C. McCain, Glen Ellyn, I1l`.',as'signor ,toV VWestern Electric Company, Incorporated, New York, N. Y., a corporation of New York Application May13, 1943, SerialY No. 486,860

6 Claims. l-

This invention relates to article working apparatus, and more particularly to a fixture for lapping quartz crystals During the manufacture of certain types of quartz crystals, such as those used as frequency control devices in electronic communication equipment, the rough crystals may be cut into slabs and the slabs lapped to the required thickness. A convenient method of lapping such slabs has been to assemble a plurality of slabs in a nest of disc shape and to interpose the nest between a pair of lapping plates, the slabs resting on the lower plate while the upper plate restson the slabs. It will be apparent then that, as the nest rotates, the slabs will be lapped on either side at substantially the same rate. Consequently, the same relative thicknesses among the slabs will be maintained throughout the lapping operation. Ii the slabs on one side of the nest are slightly thicker than those on the other, they will remain so and, since the upper lapping plate will be tipped relatively to the lower, the lapped sides of the slabs may not be parallel. To overcome this difficulty, the thicker slabs may be disposed about the nest' so as to be lapped irst. However, itis diicult to ascertain the relative thickness of the slabs with accuracy and, consequently, the lapping is both laborious and quite uncertain as to precision.

An object of the present invention is Ito provide an eifective and eilicient article working apparatus;

In accordance with one embodimentof this invention, a iixture for lapping quartz' crystals may be provided having a rotatable nest for supporting and moving a plurality of crystals between a pair of spaced lapping plates. The lower plate is fixed and the upper plate, while it rests on the crystals at the beginning of the lapping operation, is provided with a number-of adjustable supporting brackets mounted at several points on its periphery to prevent the plate from moving closer tothe xed plate than a'predetermined distance. I

Other objects land advantages of the present-` invention will be apparent from the following detailed description taken in, conjunction with i i Referring now to the drawing, a portion of a lapping` apparatus is there illustrated having a circular lapping plate IIlmounted inside'a circular container I I and resting on the base there- '1- of. -A thin disc-shaped Vnest I2, provided with a.

plurality of apertures I3 spaced in a circle therein to'receive slabs I4 of quartz, is rotatably supported immediately above the upper surface Vof the plate I0. The thickness of the nest I2 is selected itc be substantiallyless than that of the thinnest nal ydimension required in the slabs beinglapped. It` will be apparent that if too great a thickness were usedforl the nest -I2,then as the slabsA nested therein wereV lapped, eventually the nest itself-might be ground down?.4

An upper lapping plate I5 of annular shape is positioned above the nest I2 and at thebeginning of the lappingoperation this upper lapping plate rests on the upper surfaces of the quartz slabs Ill whichare assembled in the apertures I3 of the rotatable nestl I2. yAs the lapping operation proceeds and the slabs are lapped, the upper plate, bearing on the slabs, moves closer to Ithe lower plate.v In order to predetermine the minimum separation between the lapping plates and,'con sequently, the nal thickness to which the slabs will be lapped, three supporting bracket arms I6 are xed to :the upper side of the plate I5 and are equally spaced about the Aperiphery thereof, A vertically disposed, Vthreaded aperture Y I'I is formed in the outer end of each of the bracket arms I6 to receive athreaded member I8,Y the lowery end of which'is engageable with the upper surface of a cylindrical block 20, rotatably supported on a fixed shaft 2|. The shaft is mounted on arprojecting lug 22,y integrally formed with the base plate I0. By Yrotating the threaded members I8 througha knob 23, associated with each threaded member, the upper lapping plate I5 may be raised a short distance from the plate Ill and aligned therewith,v the blocks 20 serving as stop members for the threaded members I8. The clearance betweenthe threaded member I8, which threadedly engages the arm I6, and the'arm I6 maybe adjusted by a threaded member 24 which ispositioned near theY outer end of the arm I6, the outer portion ofwhich is split. The member 24, may be rotated. to move the split portions of the arm closer together to reduce the clearance between the threaded member I8 and the arm.

VGuide posts 25, mounted onA the lugs 22 of the lower plate I0, extendl into yvertically disposed apertures `26 formed inthe bracket arms I6 and serve to prevent the .upper plate from being-ro..

tated as the disc I2 is rotated, as well as to guide the upper plate during vertical movement,

Rotation of the disc I2 with respect to the lapping plates I and I5, is accomplished by a power shaft 28 journalled in a bearing 29 which is, in turn, mounted on a horizontally extending beam 30, supported on a vertically mounted post 3I. The .bearing 29 and power shaft 28 may be moved up' ordown with respect to the beam 30 by a rack and pinion assembly 33 actuated by a lever arm 32. Eccentric rotation of the disc I2 is had by mounting the disc off the center of the shaft 28, as shown in Fig. 1. During the op eration of the apparatus, the power shaft 28 is lowered by the lever arm 32 to position the disc I2 slightly above the fixed plate I0.

In the operation of this apparatus, a number of gauging devices of the same thiclmess are inserted between the upper and lower plates i0 and I5, respectively, preferably near the bracket arms It, and the separation Vbetween the plates adjusted by rotating the threaded members I8-, asexplained hereinbefore. With the v"gauges inserted, the threaded member-s I8 4are adjusted so that the tips thereof, which rest 'on the upper surface 'of the rotatable blocks 20, barely Vcontacts these blocks. rfil-.his may be determined by rotating the blocks 20, the sides of 'which are knurled. if a block rotates too freely, then the associated threaded member ldoes not -rest tightly enough on the block. On the vother hand, if -a block 20 resistsA rotation-too strongly, 'the associated `threaded member I8 'should be readjusted to relieve fthe contact pressure Jthereon. It will be apparent from. the foregoing that the separation between the lapping platesmay .be exactly predetermined and 'that :by selecting gauges of the necessary thickness, the slabs may be lapped with Vahigh degree ofl 'ace-uraeyto any desired thick-ness. Whenisl-abs to -be lapped are positionedbetween 'the plates and in the apertures I3 r4formed in the d-isc I2 to r'eceive them, regardless of any'or-iginal unevenness in the relative thickness of the slabs whiohlmigl'i't ltend `to cause the slabs to be .lapped to Adile'ring thicknesses, allvslabs will-be flappedto the same thickness tor, Whentheplate 'I 5 has moved Adownward rtoward the plate `II] -to the point "vil-1ere each l'tli-rea-"ded memberlltl isfresting on -i-ts associated rotatable blocks 'with the same vpressure Aas the other members i3, the plate I5 `:can move no further 4'a-nd, consequently, Llapping lis halted.

4V#After the threaded (mem-bers -Iii Ahave been cadjus'te'd-so-thattheir tips just `contact the :upper surfacesv of the rotatable blocks 20, with `the gauges in position lbetween A[the lapping plates, afcalibrated-collar 35 mounted `on the upper portion of leach member fl 8 -isset -at Yzero I'and locked in position lby afset screw'. A fixed -plate -31 having -av sleeve 'portion -58 positioned about `the member "F8-fand extending inside the collar 35, may be Ysuitablyfrnarlied to facilitate determining itne *position 'of the-collar 35.-

'Y lThe gauges are vthen Aremoved `and the upper plate rI5 lifted to -permit insertion of the `'slabs to belapped intheapertures -If4. "llhe'nthe upper plate `I5 is-lowered. LIt is sometimesdesirable -to extend-the ithrea'dedmembeifs IB falshort-dista'nce beyond' that determined, as 'explained Lhereinbefore, order to allow -for slight 'variations 1in the lapping doperation linhe'ife'ntiin .the iuse of .lapping compound with this type ofi'apparatus. .This is easily effected -by trotating'rea'ch lof `lthe tm'embers I8 a :small vIarrlount'the calibrated collars facilitating determination of the new setting. When the slabs have been lapped to such a thickness that the threaded members I8 rest on the rotatable blocks 20, the exact thickness of the slabs may be determined and the threaded members adjusted if necessary to reduce the minimum separation between the plate I5 and the plate II), to permit further lapping of the slabs.

What is claimed is:

1. In a fixture for lapping an article, a fixed lapping plate, a movable lapping plate spaced therefrom, an adjustable member mounted on one of said plates for adjusting the minimum separation therebetween, a rotatable stop member having a stop surface at a constant relation to one of said lapping plates engaged by said adjustable member, and means for rotatably supporting said stop member, said stop member being normally freely rotatable and having its rotation impeded by the engagement thereof of said adjustable member.

2. A lapping apparatus comprising a pair of non-rotatable lapping plates, one of said lapping plates being movable relative to the other means for guiding the movable lapping plate during the lapping operation, means for moving the work between said lapping plates, and rotatable stop members having -stop surfaces in a predetermined relation to one of said lapping plates, cooperating stop members on the other of said lapping plates to engage said rotatable Vstop members to limit the movement oi said lapping platestoward each other to apredetermined distance of separation, each of said 'rotatable 'stop members being normally freely rotatable and having its rotation irnp'eded by engagement therewith of sai-d .cooperating stop member 'on said other lapping plate.

3. A lapping 'apparatus having a pair of :nonrotatable relatively movable lapping plates, means for 'guiding one toward 'the lother of said plates during the lapping operation, means for moving the work between .said lapping plates, rotatable stop members carried by one of .said lapping plates and having stop surfaces in ia predetermined relation thereto, Vcooperating stop members carried by the other lapping 'plate for engaging said rotatable stop members and limiting the .movement o'fsaidlapping plates toward each other to a predetermined distance of separation, each .o said rotatable stop members -being normally ireely rotatable and having its rotation impeded .by engagement therewith of said cooperating stop members.

4. A lapping apparatus having .a iixed lapping plate, Aa lapping plate movable tovzard .said stationary lapping plate -during 'the 'lapping .operation, means for .guiding .said movable lapping plate, means for moving the work between said lapping plates, a rset of rotatable stop members carrielby one of said'lapping plates.andlhaving stop sur-faces lin .a Apredeteiurnined :relation thereto, means for supporting 4said :rotatable stop members, a set of cooperating stop memberscarr'iedby the .other lapping .plate vfor engaging said .rotatable Vstop :members `and `stopping the movementof said movable lapping plate toward saidnxed lapping plate to a predetermined .distance rif-.separation,.and means .for .adjusting onelset-of. saidrstop members, eachpf said rotatable stop members being normally freely rotatable and rhaving-.its rotation impeded -by fengagementitherewith' of one of said cooperating adjustable stop members.

=5. .FA `lapping A-e'ipparatus having :a stationary vlapping plate, a lapping plate'movable toward said stationary lapping plate during the lapping operation, means for guiding said movable plate, means for moving the work between said lapping plates, a plurality of posts having Contact surfaces thereon carried by said stationary lapping plate, rotatable stop members journaled on said posts and having surfaces engaging said Contact surfaces on said posts and having stop surfaces in a constant relation to said lapping plate, threaded members adjustably carried by said movable lapping member for engaging said rotatable Stop members for limiting the movement of the movable lapping plate toward the stationary lapping plate to a predetermined distance of separation, said rotatable stop members being normally freely rotatable and having their rotation impeded by engagement thereof with said threaded members.

6. In an apparatus for lapping an article, a fixed lapping plate, a movable lapping plate spaced therefrom, rotatable threaded members mounted on one of said plates for adjusting the minimum separation between said lapping plates, rotatable stop members engaged by said-threaded members, means for supporting said stop members, each of said rotatable stop members being normally freely rotatable and having its rotation impeded by engagement thereof with one of said threaded members, a calibrated sleeve adjustably mounted on each of said rotatable threaded members, means for securing said sleeve in adjusted position on said threaded member, and a fixed index member associated with each of said calibrated sleeves.

CECIL C. MCCAIN. 

